Big hikes in fuel prices and vehicle excise duty would have the greatest impact in reducing carbon dioxide emissions from traffic, according to an unpublished report commissioned by the UK Government.
More road tolls would cut pollution, researchers say
Increasing the price of petrol by 10% by the end of the decade and increasing road tax to £600 a year would be among the most effective ways of reducing pollution, says the report for the Department for Environment, Food and Rural Affairs (Defra).
The independent authors say introducing more road tolls like the London congestion charging scheme would also have a powerful effect.
The report now being considered by ministerial advisers is the first attempt to estimate how much carbon dioxide emissions would be reduced by a range of government policy options.
It concludes sticks would be far more effective than carrots, and emissions would be cut more quickly by hitting drivers' pockets than by waiting for technology changes.
The report seems certain to provoke a row between environment minister Michael Meacher, who is understood to be attracted by some of the proposals, and Transport Secretary Alistair Darling, who is more cautious about increasing motoring taxes.
The report criticises the narrow range in graduated vehicle excise duty (VED) introduced by Chancellor Gordon Brown, saying it is doing nothing to encourage drivers to buy cleaner cars.
It says the difference in road tax between the most and least polluting vehicles would have to be increased to £600 - around four times the current maximum rate of VED - to have a significant impact.
The report says this would discourage motorists from buying larger, more polluting ex-company cars and thus force businesses to choose more environmentally friendly vehicles when renewing their fleets.
Other measures which the report says would reduce carbon dioxide emissions include teleworking from home, driver training programmes, and compulsory auditing of company vehicle mileage and fuel usage which would force businesses to disclose their fuel efficiency.